1. Field of the Invention
The present invention relates to an apparatus for setting, unsetting, and retrieving an inflatable packer or bridge plug in a subterranean oil or gas well by using coiled tubing or remedial tubing for pumping fluids to the packer. More particularly, the invention relates to an improved apparatus for running in, setting, and retrieving an inflatable packer or bridge plug sized to set in a large diameter casing by passing the packer or bridge plug through a relatively small diameter production tubing by the use of continuous coiled remedial tubing.
2. Description of the Prior Art
Those skilled in the art relating to remedial operations associated with drilling, production, and completion of subterranean oil and gas wells have long utilized threaded remedial tubing inserted through production tubing for running in and setting an inflatable packer in engagement with the bore of a large diameter casing extending below the production tubing. More recently, continuous coiled remedial tubing has replaced threaded tubing, since coiled tubing may be more rapidly inserted into the well and may be easily passed through production tubing and related downhole equipment because its diameter is consistently the same size.
Typical remedial coiled tubing apparatus is described in the 1973 Composite Catalogue of Oil Field Equipment and Services, at page 662 (Gulf Publishing Co., Houston, Tex.), and manufactured by BOWEN TOOLS, INC. of Houston, Tex. Apparatus relating to this coiled tubing technique is more particularly described in U.S. Pat. Nos.: 3,182,877 and 3,614,019.
The need frequently arises in remedial or stimulation operations to pass an inflatable packer or bridge plug through small diameter restrictions; e.g., 31/2 inch production tubing, then inflate the packer in a relatively large diameter casing; e.g.; 7-inch casing, subsequently deflate the packer or bridge plug, and then retrieve the packer or bridge plug to the surface through the small diameter tubing. Recent advances, such as those disclosed in U.S. Pat. No. 4,349,204 enable inflatable packers or bridge plugs to pass through small diameter tubing, effectively seal with an enlarged-diameter casing, and then be retrievable to the surface through the small diameter tubing.
When it is desired to insert an inflatable bridge plug, a problem arises in maintaining circulation between the tubing bore and the annulus during run-in. Also, fluid pressure above and below the inflated packing element should be equalized prior to initiation of the deflation operation.
Another significant problem in the art relates to the securement of the operating mandrel of the retrievable packer or bridge plug. In prior constructions, such operating mandrel must be moved upwardly by the coiled tubing in order to effect the deflation of the inflatable elements of the inflatable packer or bridge plug. This necessarily means that set screws have to employed to effect the securement of the end of the coiled remedial tubing to the operating mandrel and thus a definite limit is imposed on the amount of tensile stress that can be placed on the coiled tubing. At the same time, when the inflatable elements are inflated into sealing engagement with the casing wall, and particularly in the case of a bridge plug, a substantial upward force may be exerted on the operating mandrel due to fluid pressure developed in the well.
In the apparatus described in my aforementioned co-pending parent Application, shear screws were utilized to effect the securement of the operating mandrel to the body of the inflatable packer carrying the expanded elastomeric sealing elements. If sufficiently strong shear screws are applied to hold the mandrel to the body against the potential upward pressure forces developed in the well bore, the same shear screws must be sheared by tension applied through the coiled remedial tubing, and this fact severely limits the number and strength of the shear screws employed to anchor the operating mandrel against upwardly directed fluid pressure forces when the retrievable bridge plug or packer is set.
It is accordingly an object of the present invention to overcome the aforementioned deficiencies of retrievable bridge plugs or packers utilizing inflatable packing elements.